Evaluation of Ascospore Prediction Model for Circular Leaf Spot caused by Mycosphaerella nawae of Persimmon

Abstract

Circular leaf spot(CLS) disease causes considerable economic damage to persimmon(Diospyroskaki) in South Korea. Mycosphaerella nawae ascospores are the primary inoculum for CLSepidemics. In this study, we investigated the seasonal fluctuation of spore release and itsrelationship to environmental factors, based on spore trapping. We evaluated the seasonal patternof released M. nawae ascospores in South Korea. During three persimmon growing seasons(2010to 2012), we recorded the release of ascospores in two regions, Jinju and Gimhae, which aremajor producing regions of sweet persimmon in South Korea. The release of CLS ascosporeswas from the first week of May to the end of July. The maximum release of spores wasobserved in late June. A computer model used accumulated degree days to simulate ascosporerelease. The overall mean accumulated degree days, from 01 May to 50% ascospore release forthe observed data(1174℃ days), was not significantly different from the predicted value of1144℃ days. The mean differences between predicted and observed release percentages for thesampling periods were not significantly different from zero.